Patent GB-405338-A (GB)
Title: Improvements in or relating to apparatus for transmitting indications or movements to a distance
IPC: H05B6/06
Filed: 1932-08-05
Abstract: 405,338. Inductances. ELLIOTT BROS. (LONDON), Ltd., Century Works, Lewisham, London, and SHOTTER, G. F., 14, The Ridgeway, Friern Barnet, Middlesex. Aug. 5, 1932, Nos. 22026/32, and 23963/33 (divided on 405,043). [Class 37.] In a system for transmitting movements of a member to a distance, the member rotates or controls the position of a conducting member relatively to a coil connected to the transmission lines, the conducting member being magnetically linked with another coil connected to a source of alternating or pulsating supply. In the form shown in Fig. 3 for transmitting impulses from a continuously rotating shaft, e.g. a wattmeter shaft, the shaft carries a conducting disc 12 cut away at 14, and rotatable in the gaps between the poles of two magnet cores 1, 5, the core 1 carrying a winding 4 connected to an a.c. supply and core 5 carrying a winding 8 connected in series with windings 10 wound on cores 9 provided with gaps within which the disc 12 is also adapted to rotate. The coils 8, 10 are connected in series in the signal transmitting circuit, the coil 8 being wound in opposition to the coils 10 in order to compensate for magnetic leakage from core 1 to cores 9. In operation, each time a conducting portion of the disc 12 is brought into the gap between the cores 1, 5 eddy currents are induced to cause an alteration of the gap flux and consequently an alteration of the relative e.m.fs. in the coil 8 and the coils 10 (which e.m.fs. are equal when a cut away portion is within the gap) to cause the transmission of an impulse over the signal circuit. In this manner impulses are transmitted at a rate dependent on the speed of rotation of the shaft 13. Any known kind of receiver, e.g. a step-by-step mechanism, which is operated at the speed of the transmitted impulses may be employed. The winding 4 may be supplied through a voltage regulating auto-transformer, the secondarycircuit of which includes an inductance and capacity which eliminates the higher harmonics in the current wave and renders the transmitter indications independent of variations in the supply frequency. The inductance and capacity are preferably arranged to tune the secondary circuit to a frequency below the supply frequency. The coils 8, 10 may operate a transmitting relay through rectifiers. The apparatus may be adapted for transmitting the positions of a member by shaping the member 12 so that it moves gradually into and out of the gaps on the cores 9. In a modification, two cores only are provided, the gaps being arranged in juxtaposition in the same plane so as to accommodate a rotatable disc which is eccentrically mounted. A pole-piece on each core carries a coil, the coils being connected in series in the transmitting circuit. Instead of a disc, a laterally movable conducting sheet, which may be triangular, may be employed. In a further form, the rotatable conducting member is in the form of a singleturn coil which moves in the gaps of two cores which may be magnetically shielded. Upon rotation of the coil, eddy currents are induced therein by the alternating flux produced on the energized core, the eddy currents generating a flux in the second core to produce impulses in the transmitting coil wound thereon.